Light-sensitive tube



p 1.935- H. H. GEFFCKEN ET AL 2,015,520

LIGHT SENS ITIVE TUBE Filed July 25, 1950 /n Venfors: Heinrich HermannGeffcken Hans Rude/F Richter Attorney Patented Sept. 24, 1935 UNITEDSTATES PATENT OFFIQE LIGHT- SENSITIVE TUBE rationof New York ApplicationJuly 25, 1930, Serial No. 470,689

In Germany July 29, 1929 4 Claims.

This invention relates to light-sensitive tubes of the kind in whichvariations of an electric current are produced by variations inillumination and in which the light-sensitive part is constituted by acomparatively large surface. This is for instance the case with theusual selenium and photo-electric tubes. The invention consists in thisthat tubes of the kind referred to are provided with a light-dispersingmember which is firmly built therein, which light-dispersing memberdistributes the incident light as uniformly as possible on thelight-sensitive layer. It has been found that in this way a substantialincrease in the performance and in the life of such tubes is obtained.

The light-dispersing member according to the invention which member isfirmly connected with the tube may be provided either on the inside oron the outside of the latter. It is often of special advantage toprovide the said member in the interior of the tube in order to obtain avery intensive uniform distribution of light over the wholelight-sensitive surface also in the case of tubes which, with theexception of a comparatively small inlet opening for the light, arecoated practically over the whole inner surface with a lightsensitivecoating. The dispersing member may in some cases be itself coated with alight-sensitive layer.

Various forms of construction according to the invention'are illustratedby way of example in the accompanying drawing, which for the sake ofsimplicity has been shown as being photo-' electric tubes of the kindproposed by Elster and Geitel, it being of course understood that theinvention is also applicable to selenium cells or the like.

The invention will become more apparent from the following detaileddescription taken in reference to the accompanying drawing, in which areshown several photoelectric tube constructions embodying the principleof the invention.

Figure 1 shows a photoelectric tube with a dispersing lens structurallycombined therewith.

Figure 2 is a similar embodiment to Figure 1 using a concentrating lens.

Figure 3 shows another form in accordance with the inventionillustrating a plurality of lens elements structurally combined with thetube vessel for uniformly distributing the incoming beam over the lightsensitive layer.

Figure 4 illustrates a further embodiment of the invention comprising adispersing member disposed inside the tube.

Figure 5 illustrates another mode of execution of the inventioncomprising a dispersing member forming a re-entrant portion of the tube.

Similar numbers identify or denote similar parts throughout thediiferent views of the drawing. 5

Figure 1 illustrates a photo-electric tube in cross section in which theparts of the inner wall of the vessel 5, which are covered with thelightsensitive layer, have been indicated in section lines. 2 is theanode which is arranged in the usual way. On the window 3 which isprovided for the inlet of the light, there is firmly cemented thedispersing lens 4. The light which falls upon the tube in the directionof the arrows is in consequence thereof'dispersed and distributed overthe whole light-sensitive surface.

In the form of construction illustrated in Figure 2, the same result isobtained by this that the glass vessel i is provided at the windowintended for the inlet of the light, with a lens-like thickened part 5,when the lens thus produced has a sufficiently short focal length.

In the form of construction illustrated in Figure 3 the same effect isagain obtained by this that the window for the inlet of the light isprovided with a number of papillary glass protuberances 5 directedinwards and outwards, each one of which acts as a small lens. Anarrangement with such a number of lens-like glass protuberances thus hasoften the advantage that the distribution of the incident light upon thewhole of the light-sensitive surface in the interior of the tube is moreuniform than in the case of an ar-- rangement with one single lensmember, as shown in Fig. 2.

Almost perfect uniform distribution of light although involving greatloss of light is obtained if the window 3 is made of milk glass.

Figures 4 and 5 show two forms of construction according to theinvention in which the dispersing member is provided in the interior ofthe tube, the same being mechanically connected with the anode in Fig. 4and with the carrier of the light-sensitive layer in Fig. 5. The firstconstructional form can be easily produced from a technical point ofview and is therefore very cheap, whilst the second one is very stableand therefore it can be used with advantage in those cases where it isnot possible to avoid mechanical vibrations of the tube (talking filmsand the like). In Fig. 4 the dispersing member 1 consists of a glassbead which is for instance provided with fiutings with the exception ofthe polished surface 8 which faces the opening 3 for the inlet .of thelight. The wire loop 2 which acts as the anode is placed round the saidglass bead. In Fig. 5 the dispersing member according to the inventionconsists of a conical re-entrant portion 9 of the vessel 1 of the tube,which re-entrant portion is coated with the light-sensitive layer likethe adjacent parts of the wall of the tube. In this form of constructionthe dispersing member also permits of obtaining at the same time anincrease in the total effective light-sensitive surface, since the lightfalling in the direction of the arrows is distributed over a largersurface before any further reflection, owing to the inclination of theconical surface s. Instead of covering the reentr-ant portion with alight-sensitive layer, the same may be mirrored on the inside or on theoutside or may be made such as to produce a diffuse-d reflection. Bysuitably changing the form of the cone 9 (by giving different curvatureto the surface) any desired distribution of the reflected rays may beobtained.

The increase in the life and load capacity of the tube according to thepresent invention can be explained as follows: The illuminated parts ofthe light-sensitive layer are subjected to a change or to an electricdisintegration to a greater extent the more intensive the illuminationper unit surface of the light-sensitive layer. If only 'a small portionof the total light-sensitive layer is subjected to illumination, theportion in question is rendered non-sensitive after a comparativelyshort period of time and in consequence thereof the tubes become more orless useless. However if according to the invention the incident lightis distributed by means of the dispersion members of the character abovereferred to as uniformly as possible over the whole lightsensitivesurface a premature ageing of the individual points is avoided. Theageing of the lightsensitive tube takes place uniformly at all points.Naturally the ageing takes place substantially slower since thedistribution of light secured according to the invention over theindividual points of the whole of the surface is subjected to a smallload. For the same reason the tube may if desired be used for a highertotal load.

What we claim is:

1. A light-sensitive tube comprising a vessel, 5

said vessel containing a light-sensitive layer, an anode therein and alight-dispersing member secured in the interior of said vessel foruniformly distributing the light over said light-sensitive layer, saiddispersing member being carried by 10 the anode of said tube.

2. A photoelectric tube comprising an envelope, a window therein forpassing controlling light rays, a cathode consisting of a coating oflight sensitive substance covering substantially the entire innersurface of said envelope excepting said window, a cooperating anodewithin said envelope and dispersing means structurally incorporated insaid tube for uniformly distributing incident light rays oversaid'cathode.

3. A photoelectric tube comprising an envelope, a window therein forpassing controlling light rays, a cathode consisting of a thin coatingof light sensitive substance covering substantially the entire innersurface of said envelope excepting said window, an anode disposed incooperative relationship to said cathode, and dispersing meansstructurally incorporated in said window for uniformly distributingincident light rays over said cathode.

4. A photoelectric tube comprising an envelope, a window therein forpassing controlling light rays, a thin coating of light sensitivesubstance covering substantially the entire inner wall of said envelopeexcepting said window, an anode disposed in cooperative relationship tosaid cathode, and dispersing means structurally combined with said anodefor uniformly distributing incident light rays over the entire surfaceof said cathode.

HEINRICH HERMANN GEFFCKEN. HANS RUDOLF RICHTER.

